Human motion analysis systems, also known as performance analysis systems, have found increasing use in evaluating the motions of the human body. Such systems have been of assistance in analyzing athletic performance and for biomechanical and medical uses. Conventional motion analysis techniques usually involve taking video recordings of the motions of a subject, and deriving digital data representing the motions by recording the positions of highlighted skin markers or by manual marking of certain points of the body. The digital data are then analyzed by visual discrimination, comparison to the motions of other subjects or standards, and/or by computational analysis of selected motion factors.
However, motion analysis systems have been limited to the analysis of external points on the body and relatively superficial factors, such as speed, gait, angular positions of body parts, etc. They do not take into account the internal motion dynamics of individual subjects, which may be affected by such factors as physical anatomy, skeletal structure, muscle or organ condition, and other internal features.
Radiography has long been used in medical practice to evaluate internal structures, particularly bone structures and, to a lesser extent, organs and soft tissues. X-ray photographs can reveal bone fractures, dislocations, deformities, and degenerative conditions. One important medical area is analysis of the spine and joints and their response under certain stresses, positions, and/or motions. In order to compare changes to the area under study, conventional radiography utilizes visual analysis of x-ray photographs of the subject area in different positions. However, static photographs can provide only a limited amount of information and requires the medical practitioner to interpolate between photographs and to rely on memory and visual discrimination.
Dynamic evaluation of the motion of internal structures is facilitated by techniques developed in fluoroscopy and radiography. Fluoroscopy can provide an x-ray image display of a subject area undergoing motion for dynamic evaluation. Videofluoroscopy involves recording the fluoroscopic images in video form for further review. While these techniques do provide excellent tools for dynamic evaluation of motion, they have many problems and disadvantages which limit their effectiveness. Videofluoroscopy is recorded in real-time, so that high speed motions or rapid changes result in distorted or blurred images. The viewing frame is generally small, compared to standard radiographs, and is fixed once a subject in motion is recorded. Thus, detailed discrimination and accurate measurement of different areas within the viewing frame is made difficult. Repeated recordings of a subject can often be required, thereby increasing exposures to radiation. Also, dynamic evaluation in conventional fluoroscopy or cineradiography involves visual inspection and discrimination, which limits the amount of information that can be derived by the medical practitioner.